Looking for suggestions for utilities\techniques that can compare calendars

Hi All

This is maybe a bit off topic but as data migration to alternative servers\services is something many in this sub have probably done I'm hoping someone can give me some useful pointers

I'm tinkering with migrating my calendar data away from Google to a.n.other provider (for now that other provider is the same domain hosting company I use for my email, at some point I may look at a self hosted solution but not yet)

I use Thunderbird …

calendar data data migration domain email google hosting may migration point privacy servers services techniques utilities